Cooling device

ABSTRACT

The present invention relates to a device for cooling an electrode holder (1) for manual arc welding with coated electrodes, as well as the electrode (4) and the electric supply cable (5), said cable (5) being surrounded by a tube (10), and said electrode holder (1) comprising a handle (2) provided with a projecting electrode pin (11) having threads (12) and a conical tip (13), and a top part (3) having a bore (16) provided with threads (17) and arranged to receive the electrode pin (11), and a fixing hole (7) extending away from and at right angles to the bore (16) to the periphery of the top part (3), the conical tip (13) of the electrode pin (11) being adapted to urge an electrode (4) inserted in the fixing hole (7), into line or point contact with the wall of the fixing hole. According to the invention, the electrode pin (11) has a channel (15) connecting the inlet end of the tube (10) in the electrode holder (1) to the fixing hole (7) for the electrode (4), cooling gas, preferably air, which is supplied to the end of the tube (10) remote from the electrode holder (1), flowing through the tube (10) and the channel (15) in the electrode pin (11) and being caused to flow out around substantially the entire circumferential portion of the electrode (4) in the fixing hole (7) therefor, and out from said fixing hole (7).

The present invention relates to a device for cooling both the electrodeholder for manual arc welding with coated electrodes, and the electrodeas well as the electric supply cable. Cooling is effected by conductingcooling gas, preferably air, through the device.

A number of welding techniques are previously known in which, fordifferent reasons, a gas is supplied to the welding point. For example,MIG or MAG welding is performed fully or semi-automatically with awelding gun in which a wire electrode is fed from a bobbin via a feedingmechanism. The melt and the feed of material in the electric arc areprotected by an inert gas. The handle can be cooled by compressed airwhich is also used for driving the electrode feeding mechanism. Air mustunder no circumstances come into contact with the arc or the melt. Sincecompressed air and protective gas are supplied to the welding gunthrough separate conduits, no cooling is effected in accordance with themethod of the present invention.

U.S. Pat. No. 2,975,267 relates to an electric welding device with aircooling in which a portion of the supply cable is surrounded by achannel through which air from the atmosphere flows, which is intendedto cool the handle by discharging through the holes in the handle.Neither the electrode nor the electrode attachment is cooled by an airflow.

The present invention provides cooling of the components which, fromtechnical aspects, are the most essential to cool, i.e. also theelectrode attachment and the electrode. This is not the case in thedevice disclosed in U.S. Pat. No. 2,975,267. By cooling the entire cablearrangement according to the present invention, i.e. the male connectionat the power source, the entire electric supply cable, the electrodeholder as well as the electrode with the attachment, the area of theelectric conductor can be reduced by about 30%, and the electrode holdercan be reduced, for instance from 600 A to 450 A. This is not possiblewith the device according to U.S. Pat. No. 2,975,267. Moreover, thecurrent intensity can be increased by about 50% as compared with themaximum current intensity recommended by the electrode manufacturer. Noris this possible with the known device.

U.S. Pat. No. 2,935,597 relates to an electric cutting device using acarbon electrode for melting the workpiece and a vigorous air stream forblowing away the molten material. As opposed to such a vigorous airstream, the air stream from the fixing hole of the electrode accordingto the present patent application is relatively faint and the flow ofair small, viz. in the order of 20 1/min. The air stream is sufficientto form a curtain against the welding fumes immediately underneath theelectrode holder, but the air stream is so faint that it will neverreach the welding point. In the device according to U.S. Pat. No.2,935,597, the air flows in through a conduit 26 adajcent the handle 32,through the tubular member 22 and into the chamber 38 of the mountinghead 37. Here, the air flow is divided into two currents one of whichdischarges through the hole 42 at right angles to the electrode 41 andthe other of which discharges at a high velocity through the hole 44parallel to the electrode. The air flows from the chamber 38, throughthe hole 42 and into the space formed by the electrode 41, the groove 40and the ridges 39. Thus, only the circumferential surface of theelectrode located between the ridges will be cooled, i.e. no more thanabout 25% of the circumferential surface of the electrode is cooled.Since the air discharges at a high velocity through the hole 44 which isoriented parallel to the electrode, the major portion of this air streamwill flow parallel to the longitudinal direction of the electrodetowards the welding point. According to the embodiment of the presentinvention as here presented, the electrode is retained in the fixinghole by the conical tip of the electrode pin urging the electrode intoline or point contact with the opposite wall of the fixing hole. The airflows through the channel in the electrode pin into the fixing hole anddischarges around the entire circumferential portion of the electrode inthe fixing hole thereof, with the exception of said line or pointcontact area and the point contact area of the conical tip with theelectrode.

U.S. Pat. No. 2,443,592 relates to an electrode holder for high currents(>500 A). The electrode holder comprises a handle and a top part. Thetop part has a sleeve with a pair of through holes and a spring-biasedplunger having a V-shaped groove at its tip. In order to mount anelectrode in the electrode holder, a handle is depressed so as toretract the plunger in the sleeve. The holes are then exposed and theelectrode is inserted therein. When the handle is released, the springurges the plunger forwards and the electrode is clamped between theforward circumferential portion of the holes and the groove. A stream ofair is introduced through the supply pipe line and is divided into twocurrents one of which discharges through the slots in the handle and theother of which discharges through the top part in the gap between thesleeve and the plunger. The electrode then is received in the holes andthe V-shaped groove, the remaining surface of the holes being covered bythe front portion of the plunger. The remaining free surface of theholes, through which the air can leave the top part, thus is verylimited. Because of this and the gap between the sleeve and the plunger,the major part of the air will leave through the slots since the airstreams follow the line of least resistance. Thus, the air would only"leak" through the holes around the electrode on each side of the toppart.

The present invention relates to manual arc welding with coatedelectrodes, i.e. a method in which coated electrodes of varying lengthand diameter are melted down by an arc maintained between the electrodetip and a workpiece. The problem in such welding technique is, interalia, that the handle of the welding apparatus becomes excessively hotand that the electrode becomes red-hot, which means that the electrodeis burnt off, leaving a substantial part of the electrode unfit for use,which means a reduction of the use-value. The first-mentioned problem,i.e. an overheated handle, is generally solved by the welder using twoor three pairs of protective gloves against the heat from the electrodeholder. Despite this, the electrode holder must be cooled after weldingwith three consecutive electrodes and so, the electrode holder isgenerally thrown into a bucket of water, with consequent formation e.g.of steam and odours. Moreover, the strain on the electrode holder andthe attachment portion of the welding current supply cable at theelectrode holder becomes considerable, for which reason the electrodeholder must generally be discarded after about 12 hours of use.

The problem of decreased use-value can be solved by lowering the currentintensity, which however means that the melting time of the electrode isprolonged, i.e. impaired welding economy. Further, in manual weldingthere is always the problem of welding fumes rising from the weldingpoint towards the welder.

The object of the present invention thus is to overcome theabove-mentioned drawbacks in prior art welding equipments for manual arcwelding by providing a device which makes the equipment lighterinvolving ergonomic advantages, less expensive, environmentally improvedfrom the point of view of overheating, and which considerably extendsthe life of the electrode holder. Further, the invention provides in thewelding operation an air curtain protecting the welder from the weldingfumes. This is achieved by a device having the features stated in theappended claims.

A preferred embodiment of the invention will now be describedhereinbelow by an example with reference to the accompanying drawing, inwhich

FIG. 1 is a schematic perspective view of a welding equipment designedaccording to the invention,

FIG. 2 is a section of an embodiment of an electric supply cableaccording to the invention, and

FIG. 3 is a section of an electrode holder designed in accordance withthe invention.

The device according to the present invention comprises an electrodeholder 1 consisting of a handle 2 and a top part 3. Further, the devicecomprises a coated electrode 4, an electric supply cable 5 and a weldingcurrent supply assembly 6. The electrode is fixed in the electrodeholder 1 by insertion in a fixing hole 7 in the top part 3 of theelectrode holder. The cable 5 supplies in conventional manner theelectrode holder with welding current from the assembly 6.

According to the invention, the welding equipment is cooled by a gas,preferably air, which is conducted through the different components. Tothis end, the welding current supply assembly 6 is provided withsuitable means for supplying air through the cable to the electrodeholder. The cable 5 must thus be able to allow passage of the air fromthe assembly 6 to the electrode holder 1. A suitable embodiment of thecable is shown in sectional view in FIG. 2. According to thisembodiment, the cable comprises an electric conductor 8 surrounded by aninsulation 9. Outside the insulation, a tube 10 is provided so as toform a space between the inner side of the tube and the insulation, thecooling gas being conducted through this space. On account of theefficient cooling, the insulation 9 need not be as thick as inconventional welding current supply cables, but may consist only of athin, partially or completely covering protective layer. The electricinsulation with respect to the surroundings is instead provided by thetube 10.

FIG. 3 shows a section of an electrode holder designed in accordancewith the invention. In the handle 2 of the electrode holder, anelectrode pin 11 is non-rotatably fixed. The electrode pin extendsoutside the handle and has a thread 12 outside which it terminates in atip 13. The electrode pin further comprises a fixing device 14 forconnecting the conductor 8 of the supply cable to the electrode pin.Moreover, the tube 10 of the cable is connected to the handle 2 in asuitable manner. In order to permit passage of the cooling gas throughthe handle, a channel 15 is provided in a suitable manner in theelectrode pin, for instance by milling, bevelling or drilling.

The top part 3 of the electrode holder has a bore 16 and a thread 17 forreceiving the tip 13 of the electrode pin 11 and the correspondingthread 12. On a level with the bottom of the bore 16, the fixing hole 7for the electrode is formed orthogonally in the top part 3. In use, thetop part 3 is screwed on the electrode pin 11 of the handle 2, and anelectrode 4 inserted in the fixing hole 7 is clamped between the tip 13and the bottom of the bore 16. The handle 2 and the top part 3 also areso shaped that they will fit tightly to each other.

Cooling gas which is introduced through the welding current supplyassembly 6 passes through the cable 5 and into the electrode holder 1via the channel 15 in the electrode pin 11 of the handle 2 and furtherinto the top part 3. From there the gas flows out through the fixinghole 7 in the gap existing between the electrode 4 and the fixing hole7, and flows along the electrode as a conical gas curtain with an acuteangle at the handle, protecting the welder from the welding fumes. Thisgas curtain never contacts the welding point. In addition, a transversebore 18 may be provided in the top part 3 to further enhance the coolingof the electrode. A guide baffle 19 may be provided on the top part 3outside the bore 18 in order to guide the air flow through the bore 18in a suitable manner.

Thanks to the efficient cooling of both the electrode holder and theelectrode as well as the electric supply cable, welding economy isconsiderably improved with the device according to the invention. Thus,the handle can be used continuously without any need to replace thehandle because of overheating. The electrode is efficiently cooled bythe gas discharging through the fixing hole of the electrode. In thismanner, the electrode will no longer become red-hot but can be used to agreater extent, i.e. its use-value increases. Because of the efficientcooling of the cable, the current intensity can be increased, meaning adecrease of the melting time of the electrode and improved weldingeconomy. Instead of increasing the current intensity, the conductor areaof the cable may alternatively be reduced, which makes it easier tohandle the equipment.

It goes without saying that the invention is not restricted to theembodiment described above and illustrated in the drawing, but may bemodified within the scope of the accompanying claims.

We claim:
 1. A device for cooling an electrode holder (1) for manual arcwelding with coated electrodes, as well as the electrode (4) and theelectric supply cable (5), said cable (5) being surrounded by a tube(10), and said electrode holder (1) comprising a handle (2) providedwith a projecting electrode pin (11) having threads (12) and a conicaltip (13), and a top part (3) having a bore (16) provided with threads(17) and arranged to receive the electrode pin (11), and a fixing hole(7) extending away from and at right angles to the bore (16) to theperiphery of the top part (3), the conical tip (13) of the electrode pin(11) being adapted to urge an electrode (4) inserted in the fixing hole(7), into line or point contact with the wall of the fixing hole,characterised in that the electrode pin (11) has a channel (15)connecting the inlet end of the tube (10) in the electrode holder (1) tothe fixing hole (7) for the electrode (4), cooling gas, preferably air,which is supplied to the end of the tube (10) remote from the electrodeholder (1), flowing through the tube (10) and the channel (15) in theelectrode pin (11) and being caused to flow out around substantially theentire circumferential portion of the electrode (4) in the fixing hole(7) therefor, and out from said fixing hole (7).
 2. Device as claimed inclaim 1, characterised in that the supply cable (5) comprises anelectric conductor (8) with a thin, partially or completely coveringprotective layer (9) surrounded by the tube (10) which forms a sheathfor the electric conductor (8) and at the same time serves as anelectric insulation therefor.